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Styling & Customization

Gilles Colling

2025-12-15

Source: vignettes/styling.Rmd
styling.Rmd

Overview

ggguides provides styling functions to customize legend appearance without diving into ggplot2’s theme element hierarchy. The main functions are:

Font Styling with legend_style()

Font Size

Adjust the overall text size (applies to both title and labels):

p <- ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point(size = 3) +
  labs(color = "Cylinders")

p + ggtitle("Default size")
p + legend_style(size = 14) + ggtitle("size = 14")

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Default size 2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 size = 14

Font Family

Change the font family for legend text:

p + legend_style(family = "serif") + ggtitle("serif")
p + legend_style(family = "mono") + ggtitle("mono")

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 serif 2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 mono

Title Emphasis

Make the title stand out with separate size and face settings:

p + legend_style(
  size = 12,
  title_size = 14,
  title_face = "bold"
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8

Text Rotation

For legends with long category names, rotate the labels to save space:

Basic Rotation 

p_long <- ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point()

p_long + legend_style(angle = 45, hjust = 1)

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

Vertical Labels

Use 90 degrees for fully vertical text:

p_long + legend_style(angle = 90, hjust = 0.5)

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

Title Rotation

Rotate the legend title independently:

p_long + legend_style(title_angle = 90, title_hjust = 0.5) + ggtitle("Rotated title only")
p_long + legend_style(angle = 45, hjust = 1, title_angle = 90) + ggtitle("Both rotated")

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv Rotated title only 20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv Both rotated

Background and Border

Add visual containers around the legend:

p + legend_style(
  background = "#FFF3E0"
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 

p + legend_style(
  background = "#FFF3E0",
  background_color = "#FF9800"
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8

Key Size

Adjust the size of legend keys (color swatches):

p + legend_style(
  key_width = 1.5,
  key_height = 1.5
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8

Margin

Control spacing around the legend:

p + legend_style(
  background = "#FFF3E0",
  margin = 0.5
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8

Full Styling Example

Combine all styling options:

p + legend_style(
  size = 11,
  title_size = 13,
  title_face = "bold",
  family = "sans",
  key_width = 1.2,
  background = "#FFF3E0",
  background_color = "#FF9800",
  margin = 0.3
)

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8

Wrapping Legend Entries

For legends with many entries, legend_wrap() creates multi-column or multi-row layouts.

By Columns 

ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point() +
  legend_wrap(ncol = 2)

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

By Rows 

ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point() +
  legend_wrap(nrow = 2)

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

With Bottom Position

Wrapping works well with horizontal legends:

ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point() +
  legend_wrap(nrow = 2) +
  legend_bottom()

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

Customizing Legend Keys

When plot aesthetics like small point sizes or low alpha values make legend keys hard to read, legend_keys() overrides the key appearance without affecting the plot.

Enlarging Small Points 

p_small <- ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point(size = 1) +
  labs(color = "Cylinders")

p_small + ggtitle("Small points in legend")
p_small + legend_keys(size = 4) + ggtitle("Enlarged legend keys")

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Small points in legend 2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Enlarged legend keys

Removing Transparency 

p_alpha <- ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point(alpha = 0.3, size = 3) +
  labs(color = "Cylinders")

p_alpha + ggtitle("Transparent legend keys")
p_alpha + legend_keys(alpha = 1) + ggtitle("Opaque legend keys")

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Transparent legend keys 2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Opaque legend keys

Combining Overrides 

ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point(alpha = 0.3, size = 1) +
  legend_keys(size = 4, alpha = 1)

2 3 4 5 10 15 20 25 30 35 mpg wt factor(cyl) 4 6 8

Targeting Specific Aesthetics

By default, legend_keys() applies to both colour and fill legends. Target specific aesthetics with the aesthetic parameter:

ggplot(mtcars, aes(factor(cyl), mpg, fill = factor(cyl))) +
  geom_boxplot(alpha = 0.5) +
  legend_keys(alpha = 1, aesthetic = "fill")

10 15 20 25 30 35 4 6 8 factor(cyl) mpg factor(cyl) 4 6 8

Reordering Legend Entries

legend_order() changes the order of legend entries without modifying factor levels in your data.

Explicit Order

Specify the exact order you want:

p + legend_order(c("8", "6", "4"))

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 8 6 4

Using Functions

Apply functions like rev or sort to the current order:

p + legend_order(rev) + ggtitle("Reversed")
p + legend_order(sort) + ggtitle("Sorted")

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 8 6 4 Reversed 2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 4 6 8 Sorted

Other Aesthetics

Reorder legends for fill, shape, or other aesthetics:

ggplot(mtcars, aes(factor(cyl), fill = factor(cyl))) +
  geom_bar() +
  legend_order(c("8", "4", "6"), aesthetic = "fill")

0 5 10 4 6 8 factor(cyl) count factor(cyl) 8 4 6

Reversing Legend Order

For simple reversal, legend_reverse() is a convenient shorthand:

2 3 4 5 10 15 20 25 30 35 mpg wt Cylinders 8 6 4

Combining Style Functions

All ggguides functions compose with +:

ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point() +
  legend_left() +
  legend_style(
    size = 11,
    title_face = "bold",
    background = "#FFF3E0"
  )

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv 

ggplot(mpg, aes(displ, hwy, color = class)) +
  geom_point() +
  legend_wrap(ncol = 2) +
  legend_bottom() +
  legend_style(size = 10, title_face = "bold")

20 30 40 2 3 4 5 6 7 displ hwy class 2seater compact midsize minivan pickup subcompact suv

Styling Continuous Color Bars

For continuous scales, colorbar_style() customizes the color bar appearance.

Basic Usage 

p_cont <- ggplot(faithfuld, aes(waiting, eruptions, fill = density)) +
  geom_tile()

p_cont

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03

Size Adjustments

Create taller, thinner bars:

p_cont + colorbar_style(width = 0.5, height = 10, aesthetic = "fill")

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03

Horizontal Orientation 

p_cont + colorbar_style(width = 10, height = 0.5, direction = "horizontal", aesthetic = "fill") +
  legend_bottom()

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03 ### Adding a Frame

p_cont + colorbar_style(frame = TRUE, aesthetic = "fill") + ggtitle("Black frame")
p_cont + colorbar_style(frame = "#FF9800", aesthetic = "fill") + ggtitle("Orange frame")

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03 Black frame 2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03 Orange frame

Removing Ticks 

p_cont + colorbar_style(ticks = FALSE, frame = "#FF9800", aesthetic = "fill")

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03

Combined Customization 

p_cont + colorbar_style(
  width = 0.5,
  height = 8,
  frame = "#E65100",
  ticks_length = 0.3,
  aesthetic = "fill"
)

2 3 4 5 40 50 60 70 80 90 waiting eruptions density 0.01 0.02 0.03

Summary

Function Purpose Key Parameters
legend_style() Comprehensive styling size, title_size, title_face, family, angle, hjust, background, margin
legend_keys() Override key appearance size, alpha, shape, linewidth, aesthetic
legend_order() Reorder entries order (vector or function), aesthetic
legend_wrap() Multi-column layout ncol, nrow
legend_reverse() Reverse entry order None
colorbar_style() Continuous color bar width, height, frame, ticks, direction

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